Gem rocks are a unique type of rock that yield gems, rather than ore, when mined. 40 Mining is required to mine these rocks. Gem rocks take about a minute and twenty five seconds to respawn, though the rate changes depending on how many players are connected to the server. When all nearby rocks have been mined, players can hop worlds to get access to unmined rocks. The chance of mining an additional ore while wearing Varrock armour does not apply to gem rocks.

The gem received is random, so rocks are not bound to specific gems, except for the rocks found during The Tale of the Muspah. It is rare to receive more expensive gems such as rubies and diamonds with the exception of the Shilo Village ones. Gems are mined at a faster rate while wearing a charged amulet of glory and ring of wealth. Wearing a ring of wealth also gives a small chance to get two gems from one rock (a message will appear when this occurs).

A popular technique when mining these rocks is to bring a chisel and cut and fletch the gems into bolt tips, thus reducing the need to bank.
The gem rocks can also be used with the gem bag reward from Dungeoneering.

Based on the above table, this means on average the player will earn 296.723 coins per rock mined, or an average of 27.69 Crafting experience and 4.8429 Fletching experience should the player decide to create bolt tips, assuming no gems are accidentally crushed.

Based on the above table, this means on average the player will earn 263.48 per rock mined, or an average of 25.25 Crafting experience and 2.5513 Fletching experience should the player decide to create bolt tips, assuming no gems are accidentally crushed.

Prifddinas

The 8 Prifddinas gem rocks, found within the Trahaearn district, yield different gems than other gem rocks found in RuneScape. Unlike the other rocks, they do not contain uncut opal, jade and red topaz, but instead offer uncut gems up to onyx and spirit gems up to dragonstone. With a crystal pickaxe, a player can expect to mine about 336 gems per hour. With a crystal pickaxe and a charged glory, a player can mine around 600 gems an hour instead.

Based on a sample of 11,771 mined gems at the Prifddinas gem rocks with a rune pickaxe, the chance of mining each type of gem is as follows:

Tai Bwo Wannai Cleanup

A gem rock found during Tai Bwo Wannai Cleanup

Gem rocks can be found randomly while hacking jungle in the Tai Bwo Wannai Cleanupminigame. When a player discovers one, a message will appear saying: "The jungle parts to reveal a gem-rich rock". These rocks have gems encrusted on the surface, which disappear as the player mines it. The rock may be mined three times before disappearing. The colours of these gems are not an indication of which gems the player will actually mine.

The Tale of the Muspah

During The Tale of the Muspah there are gem rocks that contain only sapphires, no experience is gained from these rocks and they cannot be mined again.

Explorer's aura

Gem rocks can appear in resource dungeons reached through the explorer's aura's portal. However, the aura was removed from the game after an update.

Trivia

When a gem rock is mined, the sound made when redeeming an experience lamp is played.

One of the Prifddinas gem rocks displays a yellow gem, despite there being no mineable yellow gems in game.

In the first week of release, gem rocks in Prifddinas gave a high percentage of summoning gems and uncut onyx.